陆-海碳收支过程驱动的晚中新世气候-碳循环耦合演变机制  

On the carbon-climate dynamics driven by land-sea carbon budget during the Late Miocene

作　　者：杜金龙 田军[1] DU Jinlong;TIAN Jun(State Key Laboratory of Marine Geology,Tongji University,Shanghai 200092)

机构地区：[1]同济大学海洋地质国家重点实验室,上海200092

出　　处：《第四纪研究》2023年第6期1675-1687,共13页Quaternary Sciences

基　　金：国家自然科学基金重点项目(批准号:42030403);国家自然科学基金基础科学中心项目(批准号:42188102);国家自然科学基金青年项目(批准号:42306068)共同资助。

摘　　要：晚中新世见证了近10 Ma(1 Ma=1百万年)以来全球范围内最显著的大洋碳同位素负偏与全球气候变冷事件,两者的先后发生为研究地球表层系统中碳循环与气候耦合演化机理提供了关键的时间窗口。但是,大洋碳循环事件与全球气候变冷之间的联系却缺乏合理的解释。本研究综述前人对全球变冷和大洋碳位移事件的机制解释,提出了陆-海碳收支变化驱动两者耦合演变的新假说。借助现有模式输出,晚中新世8 Ma至6 Ma期间陆地向海洋的碳通量增加了约2.1万亿吨,主导了大洋海水碳同位素的负偏移,并通过海洋碱度和营养盐的增加促使大气二氧化碳浓度降低约25%,从而可能进一步驱动了全球变冷事件;而高纬海洋的冷却则可能通过影响海洋表面溶解泵效率,调控洋盆尺度海洋储碳模式。The Late Miocene witnessed the most significant global-scale ocean carbon isotope negative excursion(Late Miocene carbon shift,referred to as LMCS)in nearly ten million years,along with a global cooling event(Late Miocene cooling,referred to as LMC).These two events,occurring sequentially,provide a critical time window for studying the coupled evolution of carbon cycling and climate in the Earth's surface system.However,the connection between the ocean carbon cycling event and global cooling lacks a reasonable explanation.This article reviews previous interpretations of the mechanisms behind global cooling and ocean carbon isotope shifts and proposes a new hypothesis that land-to-sea carbon balance changes drove their coupled evolution.With aid of model outputs,we estimated that during the Late Miocene,approximately 2100 Gitatons of carbon were transported from land to the ocean over a period of eight to six million years.This land-to-sea carbon flux dominated the negative shift in oceanic seawater carbon isotopes.Additionally,it likely led to a reduction in atmospheric carbon dioxide concentration of about 25%by increasing ocean alkalinity and nutrient levels,potentially further driving the global cooling event.The cooling of high-latitude oceans may have influenced the efficiency of the ocean surface dissolution pump and regulated ocean carbon storage patterns at basin scales.

关 键 词：晚中新世大洋碳位移事件 晚中新世全球变冷 数值模拟 碳收支 

分 类 号：P534.621[天文地球—古生物学与地层学] P595[天文地球—地质学]